Gas humidifier

ABSTRACT

In a gas humidifier used for humidifying fuel in a molten carbonate fuel cell (MCFC), a small-size gas humidifier is achieved by carrying out a steam-generating process and a gas humidifying process by the use of the steam by using a single unit. In order to achieve this structure, a plurality of longitudinal tube plates are laminated in a thickness direction with predetermined intervals so that a heat-exchanger core ( 100 ) of a plate-fin type is prepared. Heating-use high-temperature fluid (A) is allowed to flow alternately through a plurality of spaces that are formed inside the heat-exchanger core ( 100 ) and placed side by side in the horizontal direction so as to direct a gas to be humidified (B) to another space from above to below. An injection tube ( 210 ), which is used for spraying liquid (C) that serves as a steam source, is inserted virtually horizontally along tube plates on two sides in an upper portion of each space through which the gas to be humidified (B) flows. A header pipe ( 220 ), which is used for supplying the liquid (C) to the injection tube ( 210 ), is connected to the injection tube ( 210 ) at a place apart from the heat-exchanger core ( 100 ). One portion of the gas to be humidified (B) that has been introduced into the heat-exchanger core ( 100 ) is allowed to flow outside the heat-exchanger core ( 100 ) and to contact the header pipe ( 220 ) placed outside thereof.

FIELD OF THE INVENTION

The present invention relates to a gas humidifier that is used forhumidifying fuel in a molten carbonate fuel cell (MCFC).

BACKGROUND OF THE INVENTION

In a molten carbonate fuel cell, after a fuel gas such as natural gashas been humidified by steam, the resulting gas is allowed to react witha modifying catalyst, and then supplied to a fuel cell. In this case,conventionally, the humidifying process is carried out by mixing thefuel gas at normal temperature and steam generated by a boiler in a unitseparated from the boiler.

In the conventional humidifying process of this type, two units, thatis, the boiler and a mixing device, are required, inevitably resultingin a large-size facility. In order to solve this problem, there havebeen strong demands for a gas humidifier that is developed so as tocarry out a steam-generating process and a process for mixing thegenerated steam and the fuel gas by using a single unit.

The objective of the present invention is to provide a small-size gashumidifier which can effectively execute the steam-generating processand the humidifying process by the generated steam and the fuel gas byusing a single unit.

DISCLOSURE OF THE INVENTION

In order to achieve the above-mentioned objective, a gas humidifier ofthe present invention is provided with a heat-exchanger core of aplate-fin type in which a plurality of longitudinal tube plates arelaminated in a thickness direction with predetermined intervals so thata plurality of spaces, aligned side by side in the horizontal direction,are formed, with heating-use high-temperature fluid being allowed toflow alternately through those spaces, so as to direct a gas to behumidified to another space from above to below, an injection tube thatis inserted virtually horizontally along tube plates on two sides in anupper portion of each space so as to spray a liquid that serves as asteam source into the space in which the gas flows from above to below,and a header pipe that is connected to the injection tube at a placeapart from the heat-exchanger core so as to supply the liquid to theinjection tube.

In the gas humidifier of the present invention, the heating-usehigh-temperature fluid is allowed to flow through one of spaces of thetwo kinds that are formed in the heat-exchanger core, while a gas to behumidified is allowed to flow from above to below through the otherspace, and the liquid serving as a steam source is supplied to the upperportion thereof through the injection tube. With this arrangement, theliquid evaporates to form steam and the steam is mixed with the gas tobe humidified so that the gas is humidified. Here, since the headerpipe, which supplies the liquid serving as a steam source to theinjection tube, is apart from the heat-exchanger core so that it becomespossible to effectively prevent vapor locking or the like, andconsequently to stably supply the liquid.

More preferably, one portion of the gas to be humidified that has beenintroduced to the upper portion of the space is allowed to flow outsidethe heat-exchanger core and to contact the header pipe placed outsidethereof. With this arrangement, the header pipe is cooled off byutilizing the gas so that it becomes possible to supply the liquid morestably.

The clearance between the heat-exchanger core and the header pipe ispreferably set in a range from 100 to 300 mm. When the clearance is tooshort, it is not possible to sufficiently prevent vapor lock or thelike. In contrast, when the clearance is too long, it is not possible toprovide appropriate compactness.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a side view that shows a gas humidifier in accordance with oneembodiment of the present invention.

FIG. 2 is a plan view of the gas humidifier.

FIG. 3 is a bottom view of the gas humidifier.

FIG. 4 is a longitudinal cross-sectional side view that shows aheat-exchanger core in the gas humidifier of FIG. 4.

FIG. 5 is a lateral cross-sectional plan view of the heat-exchangercore.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to Figures, the following description will discuss embodimentsof the present invention.

A gas humidifier of the present embodiment is used for a fuelhumidifying process in a molten carbonate fuel cell (MCFC). This gashumidifier is constituted by a heat-exchanger core 100 having aplate-fin-type heat exchanger as its basic structure and a water-supplymechanism 200 that supplies water C into the heat-exchanger core 100 asa steam source.

The heat-exchanger core 100 is basically constituted by a rectangularparallelepiped core main body 110 composed of a longitudinalplate-fin-type heat exchanger, a derivation header 120 for heating-usegas A that is attached to the upper face of the core main body 110, anintroductory header 130 for heating-use gas A that is attached to thelower face of the core main body 110, an introductory header 140 forfuel gas B that is attached to the upper front face of the core mainbody 110 and a derivation header 150 for fuel gas B that is attached tothe lower rear face of the core main body 110. The derivation header 120and the introductory header 130 have a dome shape, and the introductoryheader 140 and the derivation header 140 have a vault shape, and each ofthese is directly attached to the core main body 110.

The core main body 110 is provided with a number of perpendicular tubeplates 111 that are placed side by side in the horizontal direction withpredetermined intervals and a pair of front and rear spacer bars 112that are placed between these so as to form a fluid flowing space in thelongitudinal direction between the adjacent tube plates 111.

The fluid flowing space has a structure in which a perpendicular firstspace 113A, which allows high-temperature heating-use gas A used forevaporating water C to flow from below upward, and a perpendicularsecond space 113B, which allows fuel gas B to be humidified to flow fromabove downward together with humidifying steam, are alternatelylaminated in the aligned direction of the tube plates 111.

In the first space 113A, perpendicular corrugated fins 114, formed asrepetitive recessed portions and protruding portions in the horizontaldirection, are placed over the full height. Thus, the first space 113Aallows the derivation header 120 and the introductory header 130 tocommunicate with each other. In the second space 113B, perpendicularcorrugated fins 115 are placed except for upper and lower portions andfor another one portion. In the upper and lower portions of the secondspace 113B, horizontal corrugated fins 116 are placed so as to allow theintroductory header 140 and the derivation header 150 to communicatewith each other. A vacant space 118, which is formed by removing thefins, is prepared on the upper portion of the corrugated fins 115 sothat an injection tube, which will be described later, is inserted tothis vacant space 118.

A water-supply mechanism 200, which supplies water C used for generatingsteam into the heat-exchanger core 100, is provided with a plurality ofinjection tubes 210 that are horizontally inserted to the respectivevacant spaces 118 inside the second spaces 113B from the rear face sideof the core main body 110 and horizontal header pipes 220 that areconnected to the injection tubes 210 at the right angle. The respectiveinjection tubes 210 are inserted to the vacant spaces 118 virtually overthe full length thereof, and a plurality of nozzle holes are formed onthe lower face of the insertion portion with predetermined intervals.

The rear portion of each injection tube 210 protrudes toward the rearface side of the core main body 110 through a through hole formed ineach spacer bar 112, and the protruding portion is connected to a headerpipe 220 having a cylinder shape, which is placed apart from the coremain body 110 on the rear face side of the core main body 110. Here,each of the protruding portions is housed in a laterally elongated case230 placed between the rear face of the core main body 110 and theheader pipe 220. Here, the inner diameter of the through hole to whicheach of the injection tubes 210 is inserted is made sufficiently greaterthan the outer diameter of each of the injection tubes 210. Thus, thecase 230 is allowed to communicate with each vacant space 118 through aring-shaped gap formed on the periphery of each injection tube 210.

The following description will discuss functions for the gas humidifierin accordance with the present embodiment.

In the core main body 110 of the heat-exchanger core 100,high-temperature heating-use gas A is introduced into the perpendicularfirst spaces 113A from below, and allowed to flow from below upward.Moreover, normal-temperature fuel gas B to be humidified is introducedinto the perpendicular second spaces 113B from above, and allowed toflow from above downward. Here, water C is sprayed from the injectiontubes 210 in the respective upper portions of the second spaces 113B.

In this case, the perpendicular second spaces 113B have been heated to ahigh temperature together with the corrugated fins 115 and 116 placedinside thereof. For this reason, the water C that has been sprayedinside the upper portions of the second spaces 113B from the injectiontubes 210 is evaporated immediately to form high-temperature steam.Thus, the fuel gas B, which is allowed to flow through the second spaces113B from above downward, is mixed with the high-temperature steam.Consequently, a humidified fuel gas B is formed, and discharged from theintroductory headers 150.

Moreover, the header pipes 220, which supply water C to the injectiontubes 210, is separated from the rear face of the core main body 110.Since the core main body 110 has been heated to a high temperature,vapor locking or the like tends to occur, when the header pipes 220 aredirectly made in contact with the core main body 110 as in the case ofthe other headers. The amount of addition of water C to the fuel gas Bis properly adjusted in accordance with the flow rate of the fuel gas B.The flow rate of the fuel gas B is changed within a very wide range, forexample, from 10 to 100%. The problem of vapor locking tends to occurparticularly when the flow rate of the fuel gas B is reduced, with theamount of addition of water C being extremely reduced correspondingly.

However, in the gas humidifier of the present embodiment, since theheader pipes 220 are separated from the rear face of the core main body110, it is possible to effectively prevent vapor locking even when theamount of addition of water C is reduced; thus, it becomes possible tostably add water C, and also to achieve a stable mixing process of steamand a stable humidifying process.

Moreover, in the present embodiment, the inner diameter of the throughhole to which each injection tube 210 is inserted is set to a size thatis sufficiently greater than the outer diameter of each injection tube210 and a ring-shaped gap is formed between the two members. For thisreason, the comparatively low-temperature fuel gas B, introduced intothe upper portions of the second spaces 113B, is allowed to flow intothe case 230 through the gaps so that portions ranging from the rearportions of the injection tubes 210 to the header pipes 220 areforcefully cooled off. Therefore, the vapor locking is prevented moreeffectively.

INDUSTRIAL APPLICABILITY

As described above, in the gas humidifier of the present invention, aliquid serving as a steam source is supplied to spaces of core of aplate-fin type heat-exchanger through which a gas to be humidified isallowed to flow from above downward, from the upper portions thereofthrough injection tubes, and header pipes, which supply the liquid tothe injection tubes, are separated from the core; thus, it becomespossible not only to carry out a steam generating process and ahumidifying process by the use of the steam by using a single unit, butalso to achieve a stable humidifying process, even when the flow rate ofthe gas to be humidified is reduced with a reduced amount of supply ofthe liquid serving as the steam source; thus, the flow rate can bechanged within a wider range.

1. A gas humidifier comprising: a heat-exchanger core of a plate-fintype in which a plurality of longitudinal tube plates are laminated in athickness direction with predetermined intervals so that a plurality ofspaces, aligned side by side in the horizontal direction, are formed,with heating-use high-temperature fluid being allowed to flowalternately through those spaces, so as to direct a gas to be humidifiedto another space from above to below; an injection tube that is insertedvirtually horizontally along tube plates on two sides in an upperportion of each space so as to spray a liquid that serves as a steamsource into the space in which the gas flows from above to below; and aheader pipe that is connected to the injection tube at a place apartfrom the heat-exchanger core so as to supply the liquid to the injectiontube.
 2. The gas humidifier according to claim 1, wherein one portion ofthe gas to be humidified that has been introduced to the upper portionof the space is allowed to flow outside the heat-exchanger core and tocontact the header pipe placed outside thereof.
 3. The gas humidifieraccording to claim 1, which is used for humidifying fuel in a moltencarbonate fuel cell (MCFC).